WiFi to LTE Handover
The following illustration describes the WiFi to LTE handover call flow.

Step | Description |
---|---|
1 |
N4 Session is established for WiFi between SMF/IWF and UPF. The MME sends Create Session Request (relocating to 4G) to the SGW-C/cnSGW. |
2 | The SGW-C/cnSGW sends Sx Session Establishment Request (No F-TEID) to the UPF. |
3 |
IMSI-based lookup is done at SxDemux for SessMgr ID. The UPF sends Sx Establishment Response to the SGW-C/cnSGW. |
4 | The SGW-C/cnSGW sends Create Session Request to the SMF/IWF. |
5 | The SMF/IWF sends Sx Modify Request with new Uplink RB PDR to the UPF. |
6 | The UPF sends Sx Modify Response to the SMF/IWF with new TEID for Uplink data. |
7 | The SMF/IWF sends Create Session Response to the SGW-C/cnSGW. |
8 | The SGW-C/cnSGW sends Sx Modify Request to the UPF with updated Uplink FAR. |
9 |
Uplink path is established. The UPF sends Sx Modify Response to the SGW-C/cnSGW. |
10 | The SGW-C/cnSGW sends Create Session Response to the MME. |
11 | The MME sends Modify Bearer Request to the SGW-C/cnSGW. |
12 | The SGW-C/cnSGW sends Sx Modify Request to the UPF with eNodeB TEIDs. |
13 | The UPF sends Sx Modify Response back to the SGW-C/cnSGW. |
14 | The SGW-C/cnSGW sends Modify Bearer Request to the SMF/IWF. |
15 | The SMF/IWF sends tunnel switch Sx Modify Request to the UPF. |
16 |
Collapsed datapath with Sxa session is established at UPF. The UPF sends Sx Modify Response to the SMF/IWF. |
17 | The SMF/IWF sends Modify Bearer Response to the SGW-C/cnSGW. |
18 | The SGW-C/cnSGW sends Modify Bearer Response to the MME. |